Amateur-built aircraft are planes constructed by individuals or groups who are not professional aircraft manufacturers. These builders often use kits or plans to create their aircraft, which can range from simple gliders to complex powered planes. The construction process allows enthusiasts to learn about aviation and customize their aircraft to meet personal preferences. In many countries, including the United States, amateur-built aircraft must adhere to specific regulations set by aviation authorities like the Federal Aviation Administration (FAA). These regulations ensure safety and quality, requiring builders to document their construction process and demonstrate that they have completed a significant portion of the work themselves.